This invention relates to a transmitting device for the generation of a signal for communications equipment, the signal to be superimposed on a network with a network load connected to two conductors of an AC power supply network, the network load being controlled by information-containing signals.
The best known communication equipment superimposes audio frequency power line control on networks. In that system one or a few centrally-located transmitters superimpose audio frequency signals of a narrow band-width on the AC distribution network, which signals are evaluated in many receivers distributed about the network for the carrying out of orders of various types. Speed of transmission, and therefore the amount of information transmitted in a time unit, is relatively small in the case of audio frequency power line control equipment.
Also known are installations which are similar in many respects to that described below, through which, for example, the meter readings of meters distributed about the network, or information on the successful carrying out of orders in the audio frequency power line control system, can be reported back to a power plant. The report then is carried in the direction opposite to the flow of the network power; the amount of information is large and many transmitters with relatively small power are needed for the report back. These transmitters must be inexpensive, but only one or a few centrally-located receivers are needed for the report-back information, and these receivers may be expensive.
Thus it has been proposed to report the use of fixed amounts of energy, gas, water or the like, by means of orders triggered by audio frequency power network signals for the momentary coupling of an oscillating circuit between two network conductors in the individual meters, and using the signals thus produced in a receiver in the power plant which contains extremely accurately discriminating electronic filters. A transmitter of the type mentioned above and suitable for this purpose has also been described. This transmitter generates resonance oscillations in the oscillating circuit tuned to audio frequencies which fade out after a few cycles. The amplitude of the oscillations in this oscillating circuit, and in the network it feeds, is therefore not constant.
Extensive theoretical research and practical experiments have shown that for these purposes, transmitters and corresponding receivers which work with broad-band signals are better suited. Such signals can be easily separated from network interference and evaluated with the aid of noise filters and limiters. A device which is suitable for the generation of broad-band and also any narrow-band signals is described in U.S. patent application Ser. No. 863,468, filed on Dec. 22, 1977. The band-width of these signals is controlled and determined by the comparative size of the current flowing through the network load, which preferably consists of a series circuit containing an oscillating coil and a capacitor and an adjustable comparison current. If the momentary value of network voltage is taken as a further comparative value, then signals whose frequency increase and decrease in a sine wave pattern during a single half-cycle of the network frequency in a preferably audio frequency range from 2000 to 20000 Hz can be generated.
The purpose of the instant invention is to expand the scope of the above-mentioned invention with respect to safe and simple operations. The instant invention is directed to the simple generation of manifold signal forms with optimum spectral distribution or for the purpose of obtaining special code forms.